An intensive effort was directed at studying the epidemiologic, virologic, immunologic, and clinical aspects of the acquired immunodeficiency syndrome (AIDS) and related illnesses. Over 300 patients with these diseases have been enrolled in research progrmas at the NIH. A study utilizing 500 hospital employees demonstrated the low risk of infectivity with the IAD virus among hospital personnel. Studies of family groups revealed spread of infection only among sexual contacts within those groups. A cell line was developed which, following infection with the AIDS virus, gave rise to a cell line with latent AIDS virus. this latent virus could be induced with a variety of viral promoting agents including radiation and IUDR. Utilizing the technique of in situ hybridization, virus-positive cells were detected in peripheral blood, bone marrow, and semen of patients. Coculture experiments revealed that in peripheral blood the AIDS virus was contained within the T4 population. Monoclonal antibodies directed toward the envelope of the virus were developed in an effort to produce strategies to block the infectivity of the AIDS patients with AIDS or related illnesses or other forms of AIDS virus infection was a profound inability to respond to soluble protein antigen. Clinical trials of recombinant Yamma-inteferon were unsuccessful in attempting to alter the clincal course of patients with AIDS but did demonstrate that the drug had potent immunomodulatory properties when given to humans. Recombinant interleukin-2 was found to enhance immune function and decrease tumor size in patients withy AIDS and early Kaposi"s sarcoma. Two antivirals directed against AIDS virus, suramin and ribavirin and one, dihydroxypropoxymethylguanin, directed against a major infectious complications of AIDS (cytomegalovirus), were entered into initial clinical trials.